fix StateCode serialization

mirai-api-http/src/main/kotlin/net/mamoe/mirai/api/http/dto/VerifyDTO.kt

@@ -15,19 +15,17 @@ abstract class VerifyDTO : DTO {
 data class BindDTO(override val sessionKey: String, val qq: Long) : VerifyDTO()
 
 
-// 写成data class并继承DTO接口是为了返回时的形式统一
 @Serializable
-sealed class StateCodeDTO(val code: Int, var msg: String) : DTO {
-    object Success : StateCodeDTO(0, "success") // 成功
-    // object AUTH_WRONG : CodeDTO(1) // AuthKey错误, @see AuthResDTO
-    object NoBot : StateCodeDTO(2, "指定Bot不存在")
-    object IllegalSession : StateCodeDTO(3, "Session失效或不存在")
-    object NotVerifySession : StateCodeDTO(4, "Session未认证")
-    object NoElement : StateCodeDTO(5, "指定对象不存在")
+open class StateCode(val code: Int, var msg: String) {
+    object Success : StateCode(0, "success") // 成功
+    object NoBot : StateCode(2, "指定Bot不存在")
+    object IllegalSession : StateCode(3, "Session失效或不存在")
+    object NotVerifySession : StateCode(4, "Session未认证")
+    object NoElement : StateCode(5, "指定对象不存在")
 
     // KS bug: 主构造器中不能有非字段参数 https://github.com/Kotlin/kotlinx.serialization/issues/575
     @Serializable
-    class IllegalAccess() : StateCodeDTO(400, "") { // 非法访问
+    class IllegalAccess() : StateCode(400, "") { // 非法访问
         constructor(msg: String) : this() {
             this.msg = msg
         }

mirai-api-http/src/main/kotlin/net/mamoe/mirai/api/http/route/AuthRouteModule.kt

@@ -27,15 +27,15 @@ fun Application.authModule() {
                     closeSession(it.sessionKey)
                     allSession[it.sessionKey] = AuthedSession(bot, EmptyCoroutineContext)
                 }
-                call.respondDTO(StateCodeDTO.Success)
+                call.respondStateCode(StateCode.Success)
             } catch (e: NoSuchElementException) {
-                call.respondDTO(StateCodeDTO.NoBot)
+                call.respondStateCode(StateCode.NoBot)
             }
         }
 
         miraiVerify<BindDTO>("/release") {
             SessionManager.closeSession(it.sessionKey)
-            call.respondDTO(StateCodeDTO.Success)
+            call.respondStateCode(StateCode.Success)
         }
 
     }

mirai-api-http/src/main/kotlin/net/mamoe/mirai/api/http/route/BaseRoute.kt

@@ -105,19 +105,22 @@ internal inline fun Route.intercept(crossinline blk: suspend PipelineContext<Uni
     try {
        blk(this)
     } catch (e: IllegalSessionException) {
-        call.respondDTO(StateCodeDTO.IllegalSession)
+        call.respondStateCode(StateCode.IllegalSession)
     } catch (e: NotVerifiedSessionException) {
-        call.respondDTO(StateCodeDTO.NotVerifySession)
+        call.respondStateCode(StateCode.NotVerifySession)
     } catch (e: NoSuchElementException) {
-        call.respondDTO(StateCodeDTO.NoElement)
+        call.respondStateCode(StateCode.NoElement)
     } catch (e: IllegalAccessException) {
-        call.respondDTO(StateCodeDTO.IllegalAccess(e.message), HttpStatusCode.BadRequest)
+        call.respondStateCode(StateCode(400, e.message), HttpStatusCode.BadRequest)
     }
 }
 
 /*
     extend function
  */
+internal suspend inline fun <reified T : StateCode> ApplicationCall.respondStateCode(code: T, status: HttpStatusCode = HttpStatusCode.OK)
+        = respondJson(code.toJson(StateCode.serializer()), status)
+
 internal suspend inline fun <reified T : DTO> ApplicationCall.respondDTO(dto: T, status: HttpStatusCode = HttpStatusCode.OK)
         = respondJson(dto.toJson(), status)
 

mirai-api-http/src/main/kotlin/net/mamoe/mirai/api/http/route/MessageRouteModule.kt

@@ -18,12 +18,12 @@ fun Application.messageModule() {
 
         miraiVerify<SendDTO>("/sendFriendMessage") {
             it.session.bot.getFriend(it.target).sendMessage(it.messageChain.toMessageChain())
-            call.respondDTO(StateCodeDTO.Success)
+            call.respondStateCode(StateCode.Success)
         }
 
         miraiVerify<SendDTO>("/sendGroupMessage") {
             it.session.bot.getGroup(it.target).sendMessage(it.messageChain.toMessageChain())
-            call.respondDTO(StateCodeDTO.Success)
+            call.respondStateCode(StateCode.Success)
         }
 
         miraiVerify<VerifyDTO>("/event/message") {